2009-04-27

Spirit Sol 113

Yestersol's drive went splendidly, covering 88.528m. This is close to the theoretical maximum for the sol (based on the drive time), and is a new single-sol Spirit record.

"You must be happy," I tell Art. He's always complaining about not getting to drive, and now we set a record on his watch.

"Yeah, well ..." he says. "We didn't drive a hundred meters, though ...."

I roll my eyes. Some people are never satisfied.

Thisol we're going to dig a trench. The trenching sequence is mostly built already -- we're just going to reuse the one Opportunity used on sol 73, with very slight modifications, and we need to put a small wrapper around it. By the time I show up, Eric's already done most of the work. He's also already done most of the pre-trench IDD work -- it seems like a long time since I did any IDDing; I actually kind of miss it.

So I decide to kill a little time by playing with my new Sony Clie. I take a few pictures in the science meeting, and a few more in the SMSA. I get to chatting with Rich Petras, look at my watch, and realize I'm five minutes late for the activity plan approval meeting. D'oh! Time really does fly when you're having fun ....

During the meeting, Jeff Biesiadecki comes by to talk about the trenching sequence. There's a rock in front of the right front wheel that's got him a little nervous. The wheels are open on the rover side, so rocks and dirt can get in, and we have no way to articulate the wheels to make the stuff come back out. Normally they just sort of work their own way out, but Jeff sees this rock as being just the right size and shape to jam in the wheel and maybe slice through some of the cables. "That would suck bad," he says, "to use the proper engineering term."

So Jeff's suggestion is to drive backward a small distance before we start trenching. But then we won't be digging the trench where we did the pre-trenching IDD work.

"Well, you're scaring me," SOWG chair Mike Carr says. "The last thing we want to do is risk anything for the sake of this observation." Trenching in the exact same spot as we did the IDD work is not a requirement, he says, so we have a solution.

Jeff raises another concern. The rover is tilted about eight degrees right now, so it might slide while we dig. This will sort of spread out the trench, and it won't be as nice. "That will suck," Jeff says. "But it won't suck bad."

We implement Jeff's suggestions, of course, even though Eric seems to think they're a little overstated. "I like Jeff," Eric says, "but he's a doomsayer. He has a reputation at the CAM for predicting doom."[1]

Well, that's a relief. Because I'd like to keep using this thing.

[Next post: sol 117, May 2.]

Footnotes:

[1] Although, to be fair ... Jeff knew more about the rovers' mobility systems than any of the rest of the drivers, having written the low-level on-board software that drives them. He'd put them through their paces during testing and knew where all the bugs and vulnerabilities were, so it's possible part of the difference was that he was just more aware of what could go wrong. It's worth noting that as the project has gone on and we've had incidents on the surface, we've become, in many ways, more conservative -- closer to where Jeff was when the whole thing started.

It should have been telling that Jeff and Mark Maimone -- Mark having written the high-level software that sat on top of Jeff's -- who had the most experience driving the vehicles during testing, were more conservative than almost anyone else at the time.